Steam turbines



Oct. 10, 1961 H. F. wARTH 3,003,321

STEAM TURBINES I Filed Feb. 12, 1957 2 Sheets-Sheet 1 FIG. 1

INLET# IUI CONDENSER COLD FIG.2

Oct. 10, 1961 L. H. F. wAR-rH 3,003,321

STEAM TURBINx-:s

Filed Feb. 12, 1957 2 sheets-sheet 2 FIG.3

WINLET Resv.

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United States Patent 3,003,321 STEAM TURBINES Laurence Hugo FrederickWarth, Rugby, England, asslgnor to The English Electric Company Limited,London, England, a British company Filed Feb. 12, 1957, Ser. No. 639,780Claims priority, application Great Britain Jan. 31, 1955 1 Claim. (Cl.60-64) The present patent application is a continuation in part of thepatent application Ser. No. 558,960, now abandoned, of Laurence HugoFrederick Warth, assignor to The English Electric Company Limited, tiledon January 13, 1956.

I'he invention relates to condensing steam turbines the shafts of whichhave to be sealed where they pass through the housing against the flowof air into or the flow of steam out of the housing.

This sealing is usually effected by means of steam packed glands havingpockets to which steam from an external source is applied as a sealingmedium when the internal pressure of the turbine is below atmosphericpressure. In condensing turbines the sealing of these glands usuallyrequires continual adjustment of valves in operation to allow forvariations in the internal pressure of the machine, and this is doneeither by hand or automatically by means of special valves.

According to the present invention, I provide sealing means for theshaft of a steam turbine having at least one turbine housing, a rotorshaft journalled therein, and a main turbine condenser, comprising incombination: a source of sealing steam, glands mounted on the ends ofthe said turbine housing and extending Voutwardly therefrom sealing thesaid rotor shaft with respect to the said housing, pockets beingarranged in the said glands at different distances from the interior ofthe said housing, those pockets which are arranged nearer to the saidhousing being in direct fluid communication with the said main turbinecondenser, and those pockets which are arranged further away from thesaid housing being in iluid communication with the said source ofsealing steam, venting means in uid communication with the said glands,and additional pockets provided in the said glands, outwardly of thesaid pockets in fluid communication with the said source of sealingsteam, the said venting means being in fluid communication with the saidadditional pockets. Preferably, it comprises a source of sealing steam,glands mounted on the ends of the said housing sealing the said rotorshaft with respect to the said housing, and venting means, pockets beingarranged in the said glands, at least one of the said pockets being influid communication on the opposite side of the said source of sealingsteam and with the said venting means.

A needle valve is provided between a main isolating valve'- and aregulating throttle valve in the pipes connecting the source of sealingsteam to the associated pockets in the glands at both ends of theturbine.

A pressure gauge is connected to the said pipe downstream of the saidneedle valve, and this enables the operator to adjust the said needlevalve with ease and accuracy When starting up the turbine.

The regulating valves in the pipes leading from the source of sealingsteam to the associated gland pockets are initially set in conjunctionwith the said needle valve (without water yet liowing through thecondensers) to give the correct ow of steam to each gland, and tomaintain a pressure of, say, 20 p.s.i.g. at the gauge. The regulatingvalves are then locked in position. Subsequently, when starting up, theoperator has only to adjust the needle valve to maintain the reading ofthe said pressure gauge at the pressure adjusted previously.

This arrangement has proved particularly advantageous Patented Oct. 10.,1961 'ice for multi-housing turbines where one needle valve only has tobe 'adjusted instead of four or six valves as in the previousarrangements.

In order that the invention may be clearly understood and readilycarried into elect, two embodiments thereof will now be described by wayof example with reference to the accompanying drawings, in which:

FIG. 1 diagrammatically shows a simple arrangement for a single housingturbine,

FIG. 2 shows a detail of FIG. l on a larger scale,

FIG. 3 diagrammatically shows an arrangement for a multi-housingturbine.

Referring rst to FIG. 1, the single-housing turbine 1 has a shaft 2passing through a gland 3 at the high pressure end, and through a gland3 `at the low pressure end of the turbine housing.

The gland 3 at the high pressure end has three consecutive pockets; thepocket 11 in the middle of the gland is connected by a pipe 12 to themain condenser 13 of the steam turbine which has conventional means forproducing sub-atmospheric pressure in the condenser 13 indicateddiagrammatically as a spray of cold water and a pump for the condensate.

The pocket 14 nearer to the cylinder 1 is connected by a pipe 15 to anintermediate stage of the turbine so as to reduce leakage losses fromthe high pressure end of the turbine to the condenser.

The pocket 6 farther away from the housing 1 is connected on top to avent condenser denoted 5 as -a whole and to be described in more detaillater with reference to FIG. 2, and on the bottom to a pipe 7 which iscounected to a source of sealing steam (not shown) with an isolatingvalve 10, a strainer 16, a needle valve 17 and a regulating valve 8having locking means 18 arranged in said pipe 7 in succession.

From the said pipe 7 a pressure gauge 19 and a branch pipe 7 branch oifbetween the said needle valve 17 and regulating valve 8. This pipe 7leads through another regulating valve 8 having locking means 18' to apocket 26 in the gland 3 at the 10W pressure end of the housing 1,nearest to this housing. Another pocket 4 farther away from the housing1 is connected to a vent condenser 5 corresponding to the vent condenser5 of the gland 3 at the high pressure end of the cylinder 1.

Cooling water is supplied by pipe 21 to a pipe coil 20, and yisdischarged by pipe 22 (FIG. 2). Steam enters by pipe 25 and iscondensed, discharging at the bottom into a tundish 24 and hence todrain. The body is vented at 23 to atmosphere. The said pipe 25 isconnected to the top of pocket 6 at the high pressure end of housing 1or to the pocket 4 at the loW pressure end (FIG. l).

Preparatory to starting up the turbine plant according to FIG. l, theregulating valves 8 and 8 are initially set in conjunction with theneedle valve 17 to give the correct ow of steam to each gland 3, 3', andto maintain a pressure of, say, 20 p.s.i.g. at the gauge 19. Thissetting is carried out at light load and without water liowing throughthe vent condensers, so that wisps of steam at the vent can be used asan indication of correct sealing. The regulating valves 8, 8 are thenlocked in position by the locking means 18, 18', respectively.

Subsequently, when starting up, the operator has to adjust only thesingle needle valve 17 to maintain the reading of, say, 20 p.s.i.g. onthe gauge 19 in order to keep satisfactory sealing conditions at theglands 3, 3'.

The pressure in the pockets 6 of the gland 3 will then be aboveatmospheric pressure by virtue of the pressure drop of the surplus steamflowing to the vent condenser 5, which itself is at atmosphericpressure.

Referring now to FIG. 3, the high pressure housing 1 and the lowpressure cylinder 101 of a multi-housing turbine have their shafts 2 and102 respectively passing 3 t outside through glands 3, 3' Iand 103,103', respectively. 'Ihe gland 3` onthe high pressure end of the highpressure housing 1 has four poclets 6, 11, 9 and 14, the lastmentionedpocliet beingnearestltoathe housingl. 'Ihe gland 3f, at theexhaust end of the highpressure housing 1` has two pockets 6', 11', thelast mentionedv oneV being nearest to the housing-1. Y Y

TheV low pressure housingj101 is built symmetrically, the two lowpressure stagesbeing at-the-ends, 'where glands 103 and 103' havepockets-104, 126 and 104', 126 respectively, therpockets 126 and V126'beingnearest to the housing 101. Sealing steam is admitted throughastrainer 16, isolating valve and needle valve 17 to a pipe 7 havingfrom which low pressure steam is tapped oi and passed through pipe 113to a heater (not shown).

The pockets 6 and 6' of the high pressurehousing are connected, atpoints opposite the connection of these pockets to the sealing steampipes 7, 7', and to vent condensers 5, 5 ofthe kind describedhereinabove with reference to FIG. 2.

The pockets 104, 104' of the low pressure housing 101 are likewiseconnected to vent condensers 105, 105' respectively of this type. Thepockets 9, V14 at the high pressure end of the high pressure housing'lare connected to the exhaust end of the saidhousing 1V and toanintermediate stage of the said high pressure housing 1,-respectively,the saidV intermediate stage being vtapped and connected to a heater(not shown) by a pipe 115.

The operation and starting up of the gland system of this plant issimilar to that described hereinabove in detail with reference to FIG.1.v It will, however, be noted that aV single needle valve 17 serveshere for adjusting the supply and pressure of sealing steamto all fourglands 3, 3', 103103' of both thev high pressure 4 housing 1 and the lowpressure housing 101. The advantage of the invention as regardsVsimplicity of operation is accordingly even greater than in the singlehousing turbine plant according to FIG. 1.

With this arrangement, areducing Valve 27 in line with an isolatingvalve 30 arranged in a by-pass 29 bridging over the isolating valve 10and needle valve 17 is used to maintainY the pressure of 20 p.s.i.g.except for starting up and shutting down. An impulse connection 28connects the reducing valve 27 Withrthe line 107. The actual changeoverfrom needle valve 17 to reducing valve 27 or conversely is carried outby opening or closing the isolating valve 30. This arrangement is ofparticular use when the pressure of the steam supply variesconsiderably.

What I claim'as my invention and desire t-o secure by Letters Patent is:

Sealing means for the shaft of a steam turbine having Y a housing havinga high pressure end and a low pressure end, a rotor shaft journalledtherein, and a main turbine condenser, comprising a combination: asource of sealing steam, a gland mounted on the highpressure end of saidturbine housing and extending outwardly therefrom sealing the s'aidrotor shaft with respect to the said housing, annular pockets beingarranged Vin the said gland at different distances from the interior ofthe said housing, one of said pockets which is arranged furthest fromthe said housing'being in direct uid communication with said sourceofrsealing steam, an intermediate pocket being in uid communication withsaid turbine condenser, and venting means in fluid communication with apocket which is arranged further from the housing than said intermediatepocket.

References Cited inthe file of this patent 'UNrTED STATES PATENTS1,246,039 Baumann Nov. 13, 1917 1,450,421 Kavanaugh et al. Apr.V 3, 19231,757,212 Parsons et al. May 6, 1930 1,759,074 Van Rijswijk May 20, 19301,910,811 Peterson May 23, 1933 2,236,274 Riceet al. Mar. 25, 19412,332,150 Huff Oct. 19, 1943

